Oil burner control



Jan- 16, 1940 w.I H. HurcHlNs ET A1. 2,187,269

OIL BURNER CONTROL Y Filed Deo. 5, 1956 4 Sheets-Sheet l Summa/13A,

Jan 15, 1940 w. H. Hu'TcHlNs ET Al. 2,187,269

OIL BURNER CONTROL Filed DBC. 3, 1936 v 4 Sheets-Sheet 2 A al * Ulm muy Jan. 16, 1940. w..H. HUTcHlNs ET A1. 2,187,269

OIL BURNER CONTROL Filed Deo. s, 19:56 4 sheets-sheet 3 Jan 16, 1940. w. H. Hu'rcHlNs ET AL 2,187,259

OIL BURNER CONTROL Filed Dec. 5, 1956 4aSheets-vSheet 4 /65 45//0 /lIZ 40 56' `@5515 55 Y' l /52 kwil/5@ Patented Jan. 16, 1940 OIL BURNER CONTROL William H. Hutchins and Henry C. Rohr, Rochester, N. Y., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 3, 1936, Serial No. 113,962

7 Claims. (Cl. 20o-138) This invention pertains to control mechanism for heating apparatus and more particularly to what is known as master controls for operating fluid fuel burners.

Figure 6 is a sectional view taken on line 6-6 of Figure 2 and showing the stack drive.

Figure 7 is a perspective view of the whole control, parts being broken away to show the In utilizing electric motors for discharging fluid whole. l

- fuel into acombustion chamber for heating pur- Figure 8 is a diagrammatic wiring diagram poses it is necessary to provide therefor a certain illustrating the connection of the master control apparatus controlled dir ectly by the presence or and the control circuit. Y absence of heat Within the combustion chamber Our control unit consists primarily of a me- 10 or associated heat ducts which will control the tallic frame 2 roughly U-shaped in cross section, l. discharge of fuel into the furnace. as best shown in Figure 7, comprising a ilat plate There are several abnormal conditions which section 4 and two upstanding end portions G, said must be protected against in the usual operation end portions supporting between them a panel of the uid fuel burner such as instances in which 8 of insulating material upon which the majority the burner does not ignite when initially started; of the parts of the control apparatus are 15 where the flame for some reason or other is exmounted. Between the panel 8 and the plate 4 tinguished during normal operation before the is supported a plate I0 of heat insulating materoom thermostat is satised, or where there is rial, such as asbestos block, to prevent the heat a momentary current failure and to immediately from being transmitted from the combustion start the burner again in operation might cause chamber or stack to the control apparatus. In an explosion. Under any one of these conditions the central portion of the plate 4 is provided an it is necessary to provide safety means to either opening l2 through which a rod I4 projects, said stop the burner or prevent the same from operatrod being concentric within a cylinder I 6 which ing for a certain period of time until it is safe is secured to the outside face of the plate 4, the to again resume operation. outer end of the cylinder I Sbeing reduced in It is therefore the object of our invention to diameter at a point I 8 and carrying within it a provide control mechanism to accomplish the deanged disk 20 having a Small evening 22 therein sired safety features above outlined. which supports the rod I4 at a spaced point. The It isa further object of our invention' to provide rod has an enlarged Section 24 adjacent the disk a unitary assembly to be applied to a position 20 to prevent, abnormal axial movement of the 30 directly heated by the burner, for controlling pur rod. poses. Concentric with the rod and around the same It is a still further object of our invention to ls mounted a helical bimetallic coil 26, one end of vprovide a unitary master control applied to the Said COil being Secured t0 the Outer end 0f the stack of the burner for controlling the supplying rod at a point 28 by a suitable screw and the inner 35 motor. end being secured under the head of screw 30 With these and other objects in view the emwhich also secures the flanged disk 20 to the bodiments of our invention reside in the following internal diameter 0f the reduced portion 0f the specification and claims and are illustrated in th member at I8. This portion 0f the apparatus 40 accompanying drawings, in which: is adapted to project through the wall of a stack 4.

Figure 1 is a horizontal section through the 3|, the bimetallic element thereby being within control unit in its assembled position on the the stack and subject to stack temperatures and stack. l the whole unit being mounted upon the stack Figure 2 is a `vertical elevation of the control wall by a suitable ange 32. As the bimetallic unit taken on line 2-2 ol.' Figure 1. Y member 26 is heated, it tends to coil androtate u Figure 3 is a detailed view of the mercury shaft I4 which accomplishes various control funcswitch controlling the ignition showing it in a tions later to be explained. dlierent position from that of Figure 2. The end G of the supporting plate 4 has a Figures V31:1 and 3b are detail views similar to pressed-out portion`33 carryinga U-shaped mem- Flgure 3 showing the cooperating parts in diier ber 34 which assists in the supporting function on 5.

-ent positions of operation.

Figure 4 is a sectional view taken on line 4-4 of Figure 2 showing. the relay.

Figure 5 is a sectional view taken on line 5 5 of Figure 2 showing the warp switch construction.

the stack wall.

consists primarily pf four different members:` a. transformer 36, an electrically heated warp switch designated generally at 38, an ignition switch 4I)v and operating mechanism therefor, and a relay The control mechanism per se 42. These are all mounted on the insulated panel 8 as are also suitable terminal screws such as those designated at 44.

' The transformer 36 may be of any conventional design for stepping down I|0 volts .of current to some lower suitable control value. The warp switch 38 is of a type in which a bimetallic element 46 is supported at its lower end in an insulated block 48 and supports at its upper end one end of a bell crank lever 50, the opposite end carrying contact 52 and the whole lever being pivoted around a point 54. The insulating block l 48, which supports the bimetallic arm 46, is itself supported on the lower end of a bimetallic strip 58 which is parallel to the strip 46 and is sup` ported so that its warping reaction, dut to temperature changes, is opposite to that in the stripv 46, the combination of the two correcting for ambient temperatures. The upper end of the bimetallic strip 58 is riveted to a bracket 59 supported on the main supporting bracket 64. The bimetallic element 58 is provided with heat from an electric heating coil 56 mounted thereon. It is thus obvious that when heat has been applied to the heating element for some time the bimetallic element will rotate as a whole counterclockwise, as shown in Figure 5, to move toward the left hand extremity and eventually project through the opening 82 in the arm 50 which causes the bell crank to rotate. in a counterclockwise/ direction breaking the -contact between contact 52 and contact 60 which is mounted on an arm 62 riveted to the lower end of the'bimetallic element 46. 'I'hese two contacts60 and 52 are directly connected in the motor circuit.

This whole structure is supported on a bracket 64 which is held to the plate 8 by suitable bolts 66. After the warp switch has once moved out from under the bell crank arm 50 and cools, it will move back in a clockwise direction but cannot move back to its original position because the upper end is locked in opening 82. It is therefore necessary to provide some resetting means which in this case is in the form of a plunger 68 supported in the outer portion of the bracket 64 within a circular housing 10. Concentric with the plunger 68 is a helical spring 12 which presses against a circumferentially enlarged portion 14 on the plunger 68 and against the bracket 64 in the base of the housing i0 to keep the plunger in its retracted position away from the contact. The inner end of the plunger 68 has a stepped portion 16, the smaller extremity of which is adapted to be forced against the arm 62 and the step itself adapted to encounter the lower end of the arm 18 of the bell crank lever carrying contact 52. This distance on the step portion 'i6 is so constructed that theend will push contact 60 outwardly far enough so that contact 52 will not touch the same during the resetting operation but once the lever 50 is back in-position over the top of the bimetallicmember 46, contact 60 will be allowed to touch contact 52 as the plunger is retracted to its normally inoperative` jects through an opening 86 rin the supportingV bracket 64. This bracket 84 may be moved with respect to the bracket 64 and is set in its adjusted position by a threaded shaft and nut 88 vso that the length of time of operationof the warp switch may be varied by varying the amount that the bell crank lever 50 projects over the top of the warp arm 46.

As before mentioned, the rod I4 is adapted to be rotated by the bimetallic coil,26 which is affected by stack temperatures provided by combustion within the burner. through the back wall of the master control and also through a cup-shaped disk 90 which is insei-ted in an opening in the insulated panel 8. On the forward face of the panel 8 is secured a multiangular bracket 92 by suitable bolts 94, said multi-angular bracket providing two aligned openings for the end of the shaft I4, said end being of reduced diameter with respect to the rest of the rod.

Adjacent the cup member 90 and surrounding the smaller end of the rod I4 is' a anged cylindrical member 96 which is adapted to extend from the inner surface of the cup-shaped member 00 to a portion of the bracket 92 through which the outer end of the rod extends and `upon which it is press-fitted. Mounted upon this cylindrical member 96 are a plurality of washers 88 between two of which extend a helical' coil spring |00 and between the next adjacent pair are located two friction disk washers |02 having between them a rotatable arm |04. With this mounting it is evident that the helical spring |00 will tend to press the two friction disks |02 tightly against the `opposite faces of the rotatable arm |04 and cause the same to rotate Withthe shaft under'normal conditions but allow relative movement lof the two.

The angled bracket 92 has a further extended portion 94 which is again bent back at right angles through which the extreme end of the shaft I4 projects and through which a cotter pin is applied to prevent the disengagement of the apparatus. Loosely mounted upon the rod I4 between the angled bracket 92I and the extreme end thereof 94 is a substantially U-shaped bracket |08 which carries thereon clips I|0 holding a mercury contact switch H2. This movable bracket merely utilizes the end of the rod as a pivot point and has no drive connection therewith. The arm |04 which, as before mentioned,

This rod I4 extendsy is clamped between the two friction disks |02 on the shaft I4, as best shown in Figure 6, extends outwardly to the right, as viewed in Figures 2 and 3, itsposition being shown in dotted lines in the latter figure. This arm carries at its extremity a pin |03, best shown in Figure 7, the body of which is formed of an insulating material and the enlarged head |I4 being of a conducting material. As best shown in Figure '1, the angled bracket |08 carries at one end and above the arm |04 a strip of insulating material |20 to which is secured the U-shaped strap I8 between the two vertical legs of which the contact I I4 and the end of the arm |04 oscillate. Also carried on the upper leg and on the inner surface thereof of the strap IIB-is a contact H6 which combines with the conducting point ||4 of the pin l|03 to provide a suitable switch. Since this bracket |08` is freely pivoted on the end of the rod I4, this U-shaped strap assumes any position to which it is forced by movement. of the arm |04 and since the apparatus usually assumes a vertical position, as shown in Figure 2, the upper leg of the U-shaped strap I8 is normally forced against the contact |04.

Also'I associated with the st rap |I8 is a. pivoted ratchet arm |32 which is supported so that the teeth |34 ride in a slot |36 in the upper arm of the U-shaped strap H8. This ratchet means is so pivoted that the majority of its weight causes it to fall toward the rod I4 so that as the arm |04 causes the strap H8 to move upward, as viewed in Figure 2, its upper leg will ratchet against the ratchet means |34 and prevent the strap II8 from descending in case the arm |04 changes its direction of rotation under certain circumstances. rlIhe lower inside edge of the ratchet means is tapered, as shown at H5 in Figure 3, so that as the arm |04 descends the insulating portion |03 of the pin will be forced thereagainst and push the ratchet means away from the strap H8 and allow the same to fall again by gravity to its position as shown in Figure 2 which in this instance is the on position of the mercury switch. There is also carried on the outer lower face of the lower leg of the strap II8 a contact |22 which is adapted to cooperate with a stationary contact |24 supported on the base.

Figures 3a and 3b show different relative positions of the parts during a cycle of operation. In Figure 3a the stack is'cooling down and the arm |04 is rotating clockwise, the ratchet teeth |34 maintaining 'the bracket H8 in the upper position. At the instant shown in this view the insulating portion |03 contacts the tapered portion H5 of the ratchet arm |32 and any further movement will push the ratchet arm to the right about its pivot and allow bracket I I8 to fall which will allow contacts |22--I24 to make.

In Figure 3b is shown a position of the arm |04 as the burner begins to heat from cold position and as it progresses up the sloping side |I5 it allows the ratchet arm |32 to move to the left so that when |03 contacts the upper leg of bracket H8 and completes switch |I4||6 the ratchet may engage the notch in bracket II8 and ratchet over the teeth '|34 to prevent any return of the bracket H8 and the notch 40 unless it is safe to do so.

It is therefore evident that in this portion of the construction there are provided three sepa.- rate switches: (1,) the mercury switch supported on the outer end of the arm which is adapted to control the ignition circuit of the oilv burner, (2) contacts |22 and 24 which are closed when the apparatus is in its closed or inoperative position, and, (3) contacts H4 and H6 which are normally open when the device is in its inoperative or lowermost position, as shown in Figure 3, and closed in the heated or full line position shown therein. As the device rotates in a clockwise direction when bimetallic element 26 is cooling, as shown in Figure 3, the ratchet will prevent the return of the bracket |08 unless the device |03 operates to push the ratchet outI of engaged position.

A conventional relay 42 is provided, said relay being composed of a core |31 and a coil with an attractable armature |40 which is pivoted about a point |42, said pivoted member carrying thereon a plurality of arms |44 each of which has mounted thereon a contact member |46 and |48 respectively, said contacts cooperating with the two stationary contacts |50 and |52 on the base panel. l

There is also provided on the base panel a conventional fuse block |54 and fuse |56 for protective purposes. A cover |88 is applied over the l control apparatus and ts down around panel 8 and is held in position by any desired bolting means. The cover has a depression therein with an opening for the reset button 68 to project through for operation.

The operation of the device may be best explained with reference to Figure 8 which shows the connective circuit thereto. Current is supplied to the transformer 36 from suitable means |58 and the transformer thus provides a low voltage source for the main portion of the controlling circuit in which a roomr thermostat |60, located in the space to be heated, initially actuates the whole control. When its contacts are closed current is supplied to the motor relay 42 through the following circuit: Transformer 36, line |62, thermostat |60, line |64, warp switch contacts 52 and 60, line |66, contacts |22 and |24 (located on the bracket and the frame adjacent the stack switch), line |68, warp switch coil 56, line |10, relay coil 42v and line |12 back to the transformer ,36. This energizes the relay 42 whichattracts its armature |40 closing its two series of contacts |50-I46 and I52-I48. The closing of the contacts |50 and |46 closes the high voltage circuit through the motor and ignition as follows: Incoming line |58, line |14, contacts I50-I46,

line |16, line |18, oil burner motor |80, 'and line' |82 back to the incoming line. Also connected in parallel with the motor is the ignition transformer |84 and the mercury switch I I2 mounted upon the end of the rod I4. The ignition transformer of course supplies a high tension current to a spark gap |86 across which high tension sparks jump, said gap being located in proximity to the oil or gas discharged into the 'furnace At the same time that the contacts |50 and |46 are closed, contacts |52 and |48 are closedv which closes a portion of the holding circuit for the relay coil 42, the rest of the circuit being controlled by the amount of heat generated by the furnace and as the rod |4, controlled by the bimetallic coil 26, turns it will cause the lever arm |04 to rise until contact I4 closes with contact H6 which completes the holding circuit for the motor. When this happens, as can best be seen from Figure 3, the additional torque is transmitted to the arm 4 and tends to rotate the whole bracket |08 around the extension of rod I4 as a pivot. This breaks the contacts |22 and |24 which cuts out the warp switch coil 56 and prevents the warp switch from operating and also causes the mercury in the mercury switch I|2 to ow to one end of the tube opening said contacts and cutting off the ignition. As the bracket |08 rotates it travels over the ratchet teeth |34 which prevents the same from returning in case of any abnormal condition, such operation proceeding untilA the room thermostat has been satisfied which then opens its contacts and denergizes the relay to open the main circuit.

Ii' now, for example, the oil or iluid does not ignite, contacts |22 and I 24 will remain closed allowing the warp switch to heat past its limit and the bimetallic element will warp out into the opening` in the arm 50 allowing contacts 52 and 60 to open and the whole circuit to be deenergized. Supposing further that the burner is operating normally upon a call for heat and for some reason or other the ame is extinguished, the arm |04 will begin to rotate in a clockwise direction, as shown-in either Figure 3 or 8, which' breaks the circuit between contacts H4 and I I6 to deenergize the relay coil and stop the motor.

However, when the lever has returned to dotted v line position shown in Figure 3, it cams over the closes both the ignition switch and contacts |22 and |24 to'recycle the mechanism. The period however between the time of breaking the circuit between contacts IIB-H4 and mating contacts |22-I24 is sufficient to allow combustible gases to escape from the furnace avoiding the danger of explosion and causing the device to recycle. If also there is a current failure the holding contacts |48 and |52 will be opened and the device cannot again be energized until contacts |22 and |24 are allowed to meet and close the original energized circuit for the relay which allows again a time delay and a purging time for the furnace.

We claim:

1. In a control mechanism for fluid fuel burners, a panel, a rod rotatably carried therein, an

arm mounted on the rod, friction driving means between the arm and rod influencing the arm to rotate with the rod but allowing relative motion between the two, a member freely pivoted on the -rod adapted to engage the arm and switching means carried by the pivoted means whereby the arm may tilt the pivoted means to actuate the switch.

2. In a control mechanism for fluid fuel burners.' a panel, a rod rotatably mounted in the panel, a member freely rotatable on the rod, a mercury bulb switch carried by the member, an` angled member insulated from and carried by the rst named memberL said angled member having a notchon one edge, a pivoted toothed latch on the panel fitting in the notch, an arm mounted on the rod, friction connecting means between the rod and the arm, a contact on the end of the arm, a contact mounted adjacent the angled member on lthe panel and spacedcontacts on the angled member cooperating with the contact on the arm and on the panel whereby hen the arm is rotated by the rod the vario contacts change to control the burner and the pivoted arm is tilted to actuate the mercury switch, the latch preventing the return of the pivoted arm.

3. In a control mechanism ,for fluid fuel burners, a panel, a rod rotatably mounted in the l panel, a member freely rotatableon the' rod, a

mercury switch carried on the member, an arm carried by the rod, friction drive means between the rod and the arm allowing relative motion therebetween, said arm engaging a part of the pivoted member, a toothed latch pivotally mount-. ed on the panel also engaging an edge of the pivoted member and in the path of the are of movement of the arm, whereby the arm carries the pivoted member with it in one direction but the latch prevents it fromv returning upon a reversal of rotation until the arm engages the latch to push it aside and disengage the teeth from contact with .the pivoted member.

4. In a control mechanism for uid fuel burners, a panel, a rod rotatably mounted in the panel,

an arm frictionally mounted on the rod to normally rotate therewith but adapted to have relative motion thereto if necessary, a member freely pivoted on the rod located to engage the arm whereby the arm may cause the member to rotate about the axis of the rod and switch contacts carried by the arm and member and adapted to close when the arm contacts the member.

5. In a control mechanism for uid fuel burners, a panel, a rod rotatably mounted `in the panel, an arm frictionally mounted on the rod to normally rotate therewith but adapted to have relative motion thereto if necessary, a member freely pivoted on the rod located to engage the arm whereby the arm may cause the member to rotate about the axis of the rod, switchcontacts carried by the arm and member and 'adapted to close when the arm contacts the member, a stationary contact located on the panel in thel path of the member and a second contact on the member adapted to engage the stationary contact to provide additional switching.

6. In a control mechanism for fluid fuel burners, a panel, a rod rotatably mounted in the panel, an arm frictionally mounted on the rod to nor- `mally rotate therewith but adapted to have relative motion thereto if necessary, a member freely pivoted on the. rod located to engage the arm whereby the arm may cause the member to rotate about the axis of the rod, switch contacts carried by the arm and member and adapted to close when the arm contacts the member and. a toothed lever pivoted on the panel in juxtaposition to the member to engage the edge thereof for ratcheting purposes, said lever having a tapered edge within the range of movement of the arm so that the latter may force the lever away from the member and release the ratchet.

7. In a control mechanism for fluid fuel burnl ers, a panel, a rod rotatably mounted in the panel, an armI frictionally mounted on the rod to normally rotate therewith but adapted to have relative motion thereto if necessary, a member freely pivoted on the rod locatedto engage the arm whereby the arm may cause the member to rotate about the axis of the rod, switch contacts carried by the arm and member and adapted to close when the arm contacts the member, a stationary contact located on the panel in the path of the member, a second contact on the member adapted to engage the stationary contact to provide additional switching and a toothed lever pivoted on the panel in juxtaposition to the member to engage the edge thereof for ratcheting purposes, said lever having a tapered edge within the range of movement of the arm so that the latter may force the'lever away from the member and release the'ratchet.

-W'ILLIAM H. HUQICHINS.A

HENRY C. ROHR. 

